1. Field of the Invention
This invention relates to an improved apparatus and method for separating flat products such as newspapers and inserts from a stack and feeding them to a drum or other moving machine parts at high speed.
2. Art Relating to the Invention
At present, machines for handling flat products, such as newspaper insert machines, often include one or more automatic feeders for feeding the products from a stationary stack to other moving parts of the machine. One item at a time is separated from the stack, either from the top or the bottom, and transferred to a rotating drum or other moving part by a separator device housed within a product feeder. Typically, one or more product feeders are mounted above a conveyor carrying open moving pockets, and the feeders transfer products from the drum into the pockets. An example of an insert machine is shown in U.S. Pat. No. 4,723,770.
If the flat products are thin or flexible, such as paper sheets or jackets, then several engineering challenges present themselves for proper and efficient machine operation. First, one item at a time must be separated from the stack without separating or damaging the remaining items. Since sheets of paper, for example, tend to stick together when stacked due to friction and air pressure, a means of separating one sheet from the stack sometimes includes a suction device to pull one sheet away while leaving the remaining sheets in place. After separation, the item must be transferred from the stationary stack to other parts of the machine that are moving, such as a rotating drum or a conveyor.
One example of a prior art separator and feeder apparatus is shown in FIG. 1. A hopper having a table 2 holds a stack of flat products 1. A reciprocating sucker bar 6 is pivotally mounted beneath the lowermost product in the stack. One or more suckers 5 are attached to one end of the sucker bar, and the bar pivots around its other end. Note that, in this prior art device, the pivot point of the sucker bar is situated directly underneath the table and the stack.
Beneath the hopper and the sucker bar, there is mounted a rotating drum 3, which carries one or more grippers 7 around its periphery. The grippers open and close at certain, timed positions as the drum rotates (counterclockwise in FIG. 1).
In operation, as an open gripper rotates up towards the hopper, sucker bar 6 pivots upward and suction is applied to the sucker 5. The sucker approaches and then makes contact with an edge portion of the lowermost product in the hopper. As used herein, this edge portion, which is the portion closest to the drum, is called the leading edge of the product.
Next, the sucker bar 6 pivots downward, causing sucker 5 to peel the leading edge of the lowermost product away from the leading edge of the next lowermost product in the stack by suction, and to bend the leading edge of the lowermost product downward. This creates a gap between the lowermost product and the next lowermost product. Meanwhile, the gripper 7 continues to rotate toward the stack. When the gripper moves into a position immediately below the bent-down leading edge of the lowermost product, the gripper closes and grabs the leading edge. Suction is then immediately released from the sucker 5, and the gripper then pulls the product down and around a portion of the periphery of the drum 3. Subsequently, the gripper opens and releases the product into a moving pocket 4, which carries the product away for further processing.
While the above-mentioned prior art separator and feeder apparatus accomplishes the task of separating one product from a stack of products and transferring it to a rotating drum, it has certain limitations that limit the speed of operation of the machine. For example, since the sucker bar is positioned underneath the stack in the prior art, in order for the sucker to clear the leading edge of the paper in time, the sucker bar must swing down (counterclockwise in FIG. 1).
In addition, in order for the sucker bar 6 to position the leading edge of the product accurately for proper pick-up by the gripper 7, the sucker bar must pivot all the way down, such that the “final,” extended position of sucker 5 is almost touching the rotating drum. In other words, the distance that the sucker must “travel” is the entire distance between the bottom side of the lowermost product in the stack and the uppermost periphery of the drum. Since there are mechanical limits on how quickly the sucker bar can be pivoted back and forth, the necessity for the sucker to make a “full travel” limits the speed at which products can be separated from the stack and transferred to the drum. This full travel requirement also increases the amount of time that suction must be applied to the sucker, and also increases wear and tear on the sucker bar. In addition, this arrangement requires the drum to have a relatively large diameter, placing limits on the rotational speed of the drum. Consequently, the above disadvantages place an upper limit on the speed of the entire machine. It is desirable to overcome these limitations, particularly in machines such as newspaper insert machines, where extremely high speeds are required.